[G12] Proton, Electron, Positron, Photon acceptance

[John Price]

Actually, you should be more concerned if the dip were in the data.  The
simulation is perfect.  The data are sloppy.  Really sloppy.  This is,
however, a good thing, since it means that the hole is at least
partially filled in.

The mirrors used in the CC are not, by any stretch of the imagination,
optically perfect.  There are visible optical dimples all over them.
This leads to Cerenkov photons going all sorts of places they're not
"supposed" to go, which has the end result of giving us a better
efficiency in the central phi region than we ought to have.

John

On Tue, 2012-07-31 at 14:26 -0700, mpaolone at jlab.org wrote:
> Ken,
> 
> The dip is something that comes from lepton-selection process in the
> center of the sector.  It's either due to a reduced cherenkov efficiency
> there, or/and a poorer pion/lepton separation.  I have some plots showing
> this, but they are on my other computer which is still packed from the
> move.  I'll post them as soon as I am up and running.
> 
> What's more bothersome to me, is that the dip isn't represented in the data.
> 
> Also MK,
> 
> It looks like your MC beam distribution is not Bremsstrahlung.  Are you
> generating your beam as 1/E?  You could try to weight your events to make
> the MC and the data beam energy match, and see how that affects your
> proton (and t) distributions.
> 
> -Michael
> 
> 
> > MK,
> >
> > Why do you have a dip in the middle of each sector for the plot labeled
> > "phi of e+" on page 1?  (Similar for the e- on page 2).  This doesn't look
> > correct.  What happens if you don't do the preliminary cut on leptons?
> >
> > Ken
> >
> >
> > -----Original Message-----
> > From: g12-bounces at jlab.org [mailto:g12-bounces at jlab.org] On Behalf Of
> > Michael C. Kunkel
> > Sent: Tuesday, July 31, 2012 4:12 PM
> > To: g12
> > Subject: [G12] Proton, Electron, Positron, Photon acceptance
> >
> > Greetings G12,
> >
> > I seem to having issues with my acceptance and would appreciate comments.
> > Please refer to the link
> > http://clasweb.jlab.org/rungroups/g12/wiki/index.php/PEpEmGamPhase_Acceptance#Tuesday_July_31.2C_2012
> > where I have plots showing acceptance plots. The issue I am having is in
> > the proton and beam acceptance, which does not match the data, however the
> > e+e-gamma acceptance does.
> >
> > I generate my beam spectrum with a 1/e function and before I send into
> > gsim I do a preliminary cut on the leptons/photons to be kinematic angles
> > of the EC/CC. This cut is what distorts my proton, beam and t spectrum.
> >
> > Any thoughts on why?
> >
> > Thanks
> > MK
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-- 
John Price
Professor and Chair of Physics
California State University, Dominguez Hills
(310) 243-3403